PTL 1: JP-A-2016-79080 describes a production apparatus for a single crystal of gallium oxide used as a wide-gap semiconductor for a power device, and the like.
Specifically, PTL 1 describes a production apparatus for producing a single crystal of gallium oxide (particularly a β-Ga2O3 single crystal) in an oxidative atmosphere, containing a cylindrical furnace body having heat resistance, a lid member for occluding the furnace body, a heater disposed inside the furnace body, a high frequency coil heating the heater through high frequency induction heating, and a crucible heated with the heater, in which the crucible is formed of a Pt—Rh (platinum-rhodium) alloy having a Rh content of from 10 to 30 wt %, and the heater is formed of a Pt—Rh alloy having a Rh content of 30 wt %.
The production apparatus for a gallium oxide single crystal described in PTL 1 has the following advantages due to the use of the crucible and the heater that are formed of a Pt—Rh alloy.
Specifically, while a melting point of Pt as a single material is approximately 1,768° C., a Pt—Rh alloy having a Rh content of from 10 to 30 wt % has a melting point of approximately from 1,850 to 1,930° C., which is significantly higher than the melting point of gallium oxide, 1,795° C., and therefore a single crystal of gallium oxide having a high melting point can be favorably produced by using a crucible and a heater formed of the Pt—Rh alloy.
Furthermore, due to the high melting point of from 1,850 to 1,930° C. of the Pt—Rh alloy having a Rh content of from 10 to 30 wt %, a wide variety of production methods including the VB method, the CZ method, the EFG method, and the like can be applied to the production of an oxide single crystal.
In particular, the Pt—Rh alloy is an alloy of Pt, which is difficult to oxidize, and therefore the crystal growth can be performed in an oxidative atmosphere, providing such an advantage that a crystal having good quality without oxygen deficiency defects can be grown.